1. Field of the Invention
This invention relates to valves, particularly a check relief valve suited for use with corrosive fluids.
2. Description of the Prior Art
There are numerous pressure regulators and unloading valves described in the art and generally available today. These prior art valves commonly display a particular structural feature; that is, the various valves usually use coiled springs mounted along the fluid pathway. For example, see U.S. Pat. Nos. 2,422,296 to Flader et al. and 2,622,611 to Stark.
One problem with using such springs is that they partially obstruct the passage of fluid between the input and output ports resulting in a pressure drop and lowered efficiency. Further, when corrosive fluids or fluids containing abrasive materials are used, the selection of the spring materials is restricted to ensure that the springs are not attacked by the corrosive fluids or worn down by the abrasives. The requirement that the spring material be chosen according to the corrosive or abrasive properties of the fluids passing through the valve can result in higher inventory costs because several types of springs must be stocked. The competing demands of cost and durability usually result in the choice of a spring material which is a compromise between the two.
Prior art pressure regulators and unloading valves also do not provide for the flow of fluid back from the system using the pressurized fluid when an overpressure in the system occurs. Typically pressure relief valves described in the prior art provide for the diversion of high pressure fluid from the pump to a reservoir when the system has reached a certain pressure. For example, see U.S. Pat. Nos. 2,342,001 to Magnuson and 2,680,447 to Groves. Although such valves may protect against overpressuring the system by the pump, they do not provide protection to the system from an overpressure emanating from the system itself.